Friction Modelling of Servomechanical Systems with Dual-relay Feedback

In this paper, an approach to identify a model for servo-mechanical systems using dual-relay feedback is presented. The model will capture the linear dynamics of the system as well as the frictional forces affecting system, through a comprehensive friction model which includes static friction, Coulomb friction, viscous friction and the boundary lubrication velocity. This friction model is able to adequately describe the friction property when the servo system runs under both low and high velocity modes. Properties of the oscillations induced under the dual-relay will be presented, based on which, insights for the selection of the relay parameters can be drawn. A systematic set of procedures to derive all the parameters of the model will be furnished. Results from a simulation study will be presented to illustrate the practical appeal of the proposed method.